Nerves are fragile and can be damaged by pressure, stretching, or cutting. Injury to a nerve can stop signals to and from the brain, causing muscles not to work properly, and a loss of feeling in the injured area.
Nerves are part of the “electrical wiring” system that carries messages between the brain and the rest of the body. Motor nerves carry messages between the brain and muscles to make the body move. Sensory nerves carry messages between the brain and different parts of the body to signal pain, pressure, and temperature.
A ring of tissue covers the nerve, protecting it just like the insulation surrounding an electrical cable. Nerves are composed of many fibers, called axons. These axons are separated into bundles within the nerve. The bundles are surrounded by tissue layers, just like the outer tissue layer that surrounds the nerve.
Pressure or stretching injuries can cause fibers within the nerve to break. This may interfere with the nerve’s ability to send or receive signals, without damaging the cover.
When a nerve is cut, both the nerve and the insulation are severed. Sometimes, the fibers inside the nerve break while the insulation remains intact and healthy. If the insulation has not been cut, the end of the fiber farthest from the brain dies. The end that is closest to the brain does not die. After some time, it may begin to heal. New fibers may grow beneath the intact insulating tissue until it reaches a muscle or sensory receptor.
If both the nerve and insulation have been severed and the nerve is not fixed, the growing nerve fibers may form a painful nerve scar, or neuroma.